This invention relates to a liquid flow rate controller for controlling the flow rate of a liquid such as syrup or fruit or vegetable juice in which a great number of small solid particles are mixed.
In general, fresh syrup or fruit or vegetable juice often has numerous small particles of fruit or vegetable therein. In many instances, such a liquid is stored in a pressure tank which is under pressure provided by a compressed gas. A discharge pipe is connected to the tank in order to feed the liquid to a cup for a customer through a valve or cock provided at the downstream end of the pipe. A flow rate controller or regulator is provided midway in the pipe line so that the liquid can flow at a constant pressure through the pipe.
A conventional flow controller for such use has a cylindrical casing in which a piston-like valve body is slidably accommodated. The valve body is in the shape of a cup and has an orifice at its end face facing the inlet of the casing. In addition, the valve body is urged by a coil spring toward the inlet of the casing. That is, the liquid passing through the inlet pushes the end face of the valve body toward the downstream side while compressing the coil spring.
In the side wall of the casing is provided at least one outlet which is opened and closed by the downstream end of the side wall of the valve body.
When the pressure of inflow liquid is higher than normal, the valve body is so moved as to close the outlet because the pressure of liquid which has entered the valve body through the orifice of the end face thereof is lower than that of liquid in the vicinity of the inlet.
When the outlet is closed, the liquid pressure in the valve body becomes high thereby to cause the valve body to return toward the upstream side by the returning force of the coil spring. That is, the valve body is moved in the casing according to the difference in pressure between the inflow and outflow liquids to keep the flow rate of the outflow liquid constant.
However, if such a conventional liquid flow controller is used for feeding such liquid containing small solid particles as fresh juice, the small particles are apt to stick in the space between the outer surface of the valve body and the inner surface of the casing thereby to prevent the valve body from sliding smoothly in the casing. Accordingly, in this case, the flow rate of the outflow liquid discharged from the outlet of the casing cannot be kept constant.